This invention relates to luminaires used for directing light toward a specific area or surface. More particularly, this invention relates to luminaires used at workstations, for example in an office environment, that receive light reflected from workstation surfaces and that advantageously redirect that light away from a sightline of a viewer.
Task and task-ambient luminaires for workstations are well-known in the lighting industry. These luminaires are effective at providing task illumination in open office environments. Generally, they mount to open office workstation partitions (to provide, e.g., uplighting and downward task lighting) or to the underside of workstation shelves or elevated storage cabinets (to provide, e.g., only downward task lighting).
In addition to lighting horizontal work surfaces, task and task-ambient luminaires can illuminate, for example, the vertical privacy panel that extends upward from an edge of the work surface opposite the viewer. Such illumination can alleviate any shadowing of overhead ambient lighting caused by the luminaire, shelf, or storage cabinet. This illumination can also create balanced surround luminance for vertically-oriented tasks (e.g., viewing a video display terminal) in addition to traditional paper tasks.
Linear fluorescent lamps of nominal 1-inch (about 2.5 cm) diameter (“T8”) or ⅝-inch (about 1.6 cm) diameter (“T5”) are common for workstation applications. Luminaire installations typically include luminaires ranging from 2 feet (about 0.6 m) in length to as much as 8 feet (about 2.4 m) in length, each installation incorporating lamps of 2-foot (about 0.6 m), 3-foot (about 0.9 m), 4-foot (about 1.2 m), or 5-foot (about 1.5 m) length singly or in tandem, as dictated by the overall length of the lighting unit. Typically, these luminaires are positioned slightly above a viewer's seated eye height and coincident to the primary task area of the work surface.
A difficulty associated with positioning these luminaires involves the inter-reflection of light received by the underside of the luminaire from the lighted workstation surface located below the luminaire. Generally, panel-mounted and undercabinet workstation luminaires having light-colored finishes and light-colored bottom surfaces indiscriminately redirect some of the inter-reflected light toward the viewer and out of the workstation. These disadvantageously redirected light rays reduce lighting efficiency at the workstation and can distract the viewer from his/her primary tasks. Such visual distraction outside of the viewer's main task focus can cause viewer annoyance and result in visual fatigue.
A known technique for preventing the indiscriminate redirection of light rays within a workstation is to provide a luminaire with a black finish. This results in the absorption of much of the inter-reflected light rays by the luminaire. However, the absorbed light rays are wasted in that they may have otherwise contributed to lighting the workstation if not for their absorption by the black luminaire surfaces. In addition, if an entirely black luminaire is not desired (e.g., for aesthetic reasons), providing a nonreflective finish on the underside of the luminaire can increase manufacturing complexity and costs.
Accordingly, it would be desirable to be able to provide a luminaire having a surface that advantageously redirects received light away from a sightline of a viewer, is simple and cost efficient to manufacture, and which redirects at least some of the received light toward a target area.